It is nice to be remembered. What about flowers or a food basket together with a card acknowledging her work in taking care of your late brother and thanking her?

Anything other than that has a potential for a very unpleasant outcome for the person who’s trying to help (you). You never know how people will react to money issues. I say play it safe for your own peace and tranquility.

Might you involve the older daughter in some way, perhaps posing it thusly- “I’m so impressed by everything you did to care for your dad. I wonder if he would want us to care for your sister in some way?” See what ideas she might have.

Maybe. Donation to college funds for the older daughter’s children, if she has any, in an amount equal to what you wold give to the younger daughter.

Think of it, you are a virtual stranger whose only connected to them thru your brother, you have no logical reason to involve yourself in their personal financial business. The only link is your brother.

If you arbitrarily reward the one sibling who did nothing for your brother (her own father) and not the sister who took full responsibility, that's incredibly disrespectful and judgemental. You'll only end up alienating the siblings, but ruining any hope of building any relationship with either.

If you want to offer compensation for your absence anf the extra work involved in caring for your brother, talk to your niece first. Most care givers serve out of love and duty, money might be insulting to her, but maybe something like a college fund would be better. Ask how you can help her, she just lost her dad.

Your other niece is not entitled to any compensation money. Remember your only connection is for brother and she did not do anything to help him or her sister in caring for him. Don't expect that throwing money at her problems will improve anything, it won't.

She lives several hours away and visited/helped as much as possible, the older sister lived close to her dad.

I routinely help family members who don't have much -- why on earth would I feel compelled to do anything for those who are capable of doing for themselves?

If an adult child is upset because their sibling gets something and they don't, they are not good at adulting.

First daughter's check is in appreciation for all she did for your brother; she should use it for herself or give to charity in his name.
Second check is to second daughter is recognition of her father, to be used as needed.

Always treat children equally; you won't regret it.

And not worry about it. If you can't bring yourself to do that alone, then another poster's idea of acknowledgement of the better off child's efforts with a family dinner or possibly a spa pkg.

I am sorry you lost your brother, friend.